The invention relates to the technical field of the assembly of ion beam sputtering targets on a support plate.
More generally, the invention may be applied to any type of assembly between two plates having a precise spacing. This requirement to prepare an assembly between two plates, having a precise spacing, is particularly important for the sputtering targets used in all fields of application of thin films deposited under vacuum (micro-electronics, mechanical engineering, automotive, optics, flat screen, packing film, etc.).
It may be recalled, in a manner perfectly known per se to a person skilled in the art, that a physical vapour deposition takes place in a chamber at reduced pressure, with a plasma between a positive pole and a negative pole, in combination with a gas (for example argon), using either direct current, pulsed current, or high frequency current.
Reference can be made to FIG. 1, which schematically shows the main elements of a physical vapour deposition chamber.
In this example of ion beam sputtering, the positive pole consists of the walls of the chamber (A), while the negative pole consists of a sputtering target (F) which is the focus of ion bombardment. The atoms of the target (F) condense on a substrate (I) to form a thin film deposit (H). The target (F) is fixed to a support plate (D) generally associated with a cooling element (C).
The target (F) is fixed to the support plate (D) by a bonding or seal system (B).
This bond between the sputtering target and the support plate must be provided to meet certain requirements, in particular the ability to withstand a temperature of heat conduction, electrical conduction, vacuum degassing, contamination of the target, etc.
Various technical solutions have been proposed to prepare the assembly and the bond between the sputtering target and the support plate. For example, a continuous layer of solder can be used, formed between the target and the support plate.
According to the teaching of document US 2006/0266643, the bond is prepared using a thin film consisting of glue, in combination with a grid. According to document US 20060283703, the glue layer is formed of lines whereof the geometry is not indicated (width, height, length), or of parallel lines, or of network forming lines, or of lines forming concentric rings.
These various methods serve to obtain satisfactory results, but are difficult to implement. In particular, major difficulties arise for adjusting the thickness of the glue layer, for example as it appears from document WO 2006/132916. Furthermore, the glues used must provide certain specific characteristics, generally at high cost. Difficulties may also appear according to the shape and dimensions of the target used.
As it appears from document WO 2006/132916, the trapping of gas, in a layer of glue, can cause a deterioration of the solidity of the seals when placed under vacuum, by the formation of bubbles associated with the decrease in external pressure and trapped in the seal.
It is the object of the invention to remedy these drawbacks simply, safely, effectively and efficiently.